The 7th gen is precisely when "Retro Gaming" became a thing. Of course it always existed, there always were re-release collections of old games and people playing older games, but those things were super niche.
During the 7th gen, with the advant of "platforms" like the Virtual Console, is precisely when retro gaming became what it is and what we know it to be today. 8-16 bit games selling millions of copies on the Virtual Console, emerging Youtube channels on old games, the collectors market exploding, new games made in the style of old like Mega Man 9 etc all things that justified the existance of retro gaming forums like this one, that appeared during the 7th gen.
And all that was "retro gaming" as opposed to "modern gaming", meaning the 7th gen.
This is why it will never make no sense to bundle the 7th gen with older ones, retro gaming as we know it was always from the start in opposition with it.

That's of course without mentionning all the modern gaming tropes that started during the 7th gen that are still true today, because the 7th gen was precisely when technological advancement started to stall. Like the always online for everything, achievements, HD resolutions, etc Now watch as Mr "Gears of War is retro" is going to pretend that "Actually you could play Phantasy Star Online on Dreamcast and Resident Evil Outbreak online on PS2 (except in Europe!) so that's totally the exact same thing as the always online for everything of today. P.S: I watched Stranger Things so I know that kids in the 80's communicated with talkie-walkies which is exactly like smartphones today, boomers can't fool me".